In this paper I investigate a largely untold chapter in the history of race thinking in Northern Europe and North America: the transition from the form of racism that was used to justify a race-based system of slavery to the medicalising racism which called for segregation, apartheid, eugenics, and, eventually, sterilization and the holocaust. In constructing this history I will employ the notion of biopower introduced by Michel Foucault. Foucault’s account of biopower has received a great deal of attention recently, but because what he actually has to say about race tends to be vague and radically incomplete, many race theorists have been critical of his contribution. However, even if the account of the holocaust in terms of biopower is incomplete, there is still a great deal to be learned from Foucault’s identification of this biologizing, or medicalising racism.